Method for thermally conditioning preforms

Abstract

Provided is a thermal conditioning method of preforms. The method includes heating each preform by transport along a heating path exposed to heating radiation with a determined production rate; transporting the preforms (in line along a diffusion path; transforming the preforms in forming units at the determined production rate. The diffusion path includes a final buffer section along which the preforms travel for an adjustable duration.

The invention claimed is: 
     
         1 . A method for thermally conditioning preforms ( 14 ) before they are formed by stretch blow-molding, in a facility ( 100 ) for producing containers ( 12 ), the method comprising:
 at least a first step (E 1 ) of heating each preform ( 14 ) by transport along a heating path ( 66 ) exposed to heat radiation, the preforms ( 14 ) exiting the heating path ( 66 ) at a predetermined production rate (R);   a second step (E 2 ) of diffusing the heat stored in each preform during which the preforms ( 14 ) are transported in a line along a diffusion path ( 70 ) that is not exposed to the heat radiation and extends from a downstream end of the heating path ( 66 ) to a station ( 52 ) for forming the preforms ( 14 ); and   a third step (E 3 ) of transferring the preforms, following the diffusion step (E 2 ), into forming units ( 56 ) of the forming station ( 52 ) at said predetermined production rate (R),   wherein the diffusion path ( 70 ) comprises at least one final buffer section ( 70 A) that the preforms ( 14 ) travel along in an adjustable duration (Da).   
     
     
         2 . The method of  claim 1 , wherein a duration of the diffusion step (D) is controlled independently of the production rate (R) by adapting the adjustable duration (Da). 
     
     
         3 . The method of  claim 1 , wherein a diffusion duration (D) setpoint is selected, the adjustable duration (Da) being controlled automatically as a function of the production rate (R) to keep the diffusion duration (D) equal to the setpoint independently of the production rate (R). 
     
     
         4 . The method of  claim 1 , wherein the adjustable duration (Da) is controlled so that the diffusion duration (D) is identical for each preform. 
     
     
         5 . The method of  claim 4 , wherein the preforms are transported along the final buffer section ( 70 A) by shuttles ( 34 ) moved independently of each other by means of a linear motor ( 35 ). 
     
     
         6 . The method of  claim 5 , the preforms ( 14 ) travel along the final buffer section ( 70 A) with an identical speed profile. 
     
     
         7 . The method of  claim 1 , wherein the adjustable duration (Da) can adopt a plurality of values in a range delimited by a minimum lower limit and an upper limit for a given production rate (R). 
     
     
         8 . The method of  claim 7 , wherein the minimum lower limit depends on a length of the final buffer section and a maximum speed that the preform can reach at each point of the final buffer section. 
     
     
         9 . The method of  claim 7 , wherein the upper limit depends on a length of the final buffer section and the production rate (R). 
     
     
         10 . The method of  claim 1 , the production rate (R) can be controlled between a maximum rate (Rmax) and a minimum rate (Rmin) during the production of containers ( 12 ), the length of the final buffer section ( 70 A) and/or the maximum speed of the preforms ( 14 ) on the final buffer section ( 70 A) being determined so that the adjustable duration (Da) is controlled so that at least one diffusion duration (D) value can remain constant for any production rate (R) between the maximum rate (Rmax) and the minimum rate (Rmin). 
     
     
         11 . The method of  claim 1 , wherein the preforms ( 14 ) are transferred one by one in succession into the forming station ( 52 ). 
     
     
         12 . The method of  claim 1 , wherein a predetermined number of a plurality of successive preforms ( 14 ) form a group, the preforms in a single group being transferred simultaneously into the forming station ( 52 ). 
     
     
         13 . The method of  claim 12 , wherein the successive preforms ( 14 ) in a single group travel along the final buffer section ( 70 A) with different speed profiles so that the diffusion duration (D) is the same for all of the preforms ( 14 ) in the group. 
     
     
         14 . The method of  claim 1 , wherein the heating step (E 1 ) comprises two successive heating sub-steps (E 1 A, E 1 B) prior to the diffusion step (E 2 ), the two heating sub-steps (E 1 A, E 1 B) being separated by an intermediate step (E 1   int ) of transporting the preforms in a line, the heating path ( 66 ) being divided into an upstream heating section ( 66 A) and a downstream heating section ( 66 B) connected by a transition path ( 68 ). 
     
     
         15 . The method of  claim 14 , wherein the transition path ( 68 ) comprises at least one intermediate buffer section ( 68 A) that the preforms ( 14 ) travel along in an adjustable duration (Dr) that is controlled independently of the production rate (R).